ready. that means making important decisions about what he is going to be wearing today. >> being a bilateral amputee, you have to use prosthetics. if you are a single-arm amp tea, you have the ability to use a real hand to help, you know, it's kind of like a tool for them. >> near san diego, california, katie walker is putting her newest tool. this para olympic hopeful is trying out prosthetics field. >> the difference is the little wrist unit. it actually pops off. >> all right. >> and actually, the handle goes right inside of here. so, it's supposed to, after i swing, after i follow through, you just pop it right off. >> then run? >> then start running. >> and rotate around. cool.